Signaling system for railways.



IJLD. TAYLOR. SIGNALING SYSTEM FOR RAILWAYS.

APPLICATION FILED JUNE 17,19oa. RENEWBD 1120.4, 1913.

Patented J an. 20, 1914.

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SIGNALING SYSTEM FOR RAILWAYS.

APPLIOATION rILEn JUNE 17, 190e. RBNBWBD 1330.4. 191s.

wn-N Essss Patented Jan.20, 1914.

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cuits, and usually the distance of track be- ITED STATES PATENT OFFICE.

JOHN D. TAYLOR, 0F EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH AND SIGNAL COMPANY, OF SWI OF PENNSYLVANIA.

SSVALE, PENNSYLVANIA, A CORPORATION SIGNALING SYSTEM FOR RAILWAYS.

Application filed June 17, 1908, Serial No. 438,966.

To all whom t may concern:

Be it known that l, JOHN D. TAYLOR, a citizen of the United States, residing at Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improvements in Signaling Systems for Railways, of which the following is a specification.

My invention relates to automatic block signaling systems for railways which employ track circuits to control the signaling devices as to at least one ot their operations.

My invention is particularly applicable to electric railways in which the track rails are included in the return path for the car propulsion current to the generator.

Heretot'ore in many of the automatic block signaling systems insulation has been employed in one or both of the track rails to separate the signaling current in one track circuit from the adjacent track cir tween the two next adjacent insulating points has been termed a block section. Thus it will be seen that usually a block section may be said to be determined by the length ot1 track comprised in the track circuit. In the present invention insulation is not employed in the track rails to separate the signaling currents of the several track circuits, but the sources of signaling current are so arranged with regard to one another that midway between two adjacent sources there will be points of equal potential between the two rails. The distance of track, therefore, between two such pairs of points may be said to constitute a block section,7 and in this invention a signaling device will be located at about each of such pairs of points. This arrangement of points oit equal potential oit' signaling current in the track rails may be obtained by connecting the sources of signaling current to the track at intervals in such manner that alternate sources are connected in the same sense to the track, while the others are connected in an opposite sense; that is, one source will have its positive terminal connected to a given rail, while the next source on either side will have its negative terminal connected to the same rail. Connected in this way, current will tlow from any source through the rails to each of the sources on` either side and back to the first-named Speoication of Letters Patent.

Patented Jan. 20, 1914.

'Renewed December 4, 1913. Serial No. 804,761.

source. The rails will thus alternate in electric potential; that is, any rail that is positive at one source will be negative at the next source either side, and vice versa. Mid way between the sources, therefore, the potcntials of the two rails will be the same. There will be a fall of potential from the positive connection of one source to the middle point between two sources in one rail, and from the opposite middle point of the other rail to the negative of the source. Therefore, a relay connected to the rails between the equipotential point and a source will have an electromotive force impressed upon it due to the fall of potential between the points of connection of the relay and the equipotential points.

l/Vhen the automatic signaling system is used on a. railway having an electric propulsion current for the motor cars, itI is necessary to use an alternating signaling current in the track circuits so as to distinguish between the signaling current and the car pr0 pulsion current. If the car propulsion current is alternating, then the signaling cur rent must be alternating of a higher fre quency. It is well understood in the art that a relay can be so constructed as to respond to alternating current oit a giveny frequency, and not. to an alternating current of a lower frequency, or to a direct current.

In the accompanying drawings, Figure l is a diagrammatical view of a portion of an electric railway and the necessary parts and appliances for two block sections ot' an automatic signaling system embodying my invention. In this figure the parts of the signaling system are illustrated in the positions they assume with no car or train present. Fig. Q is a view similar to Fig. l, but illustrating a modification ot' my invention. Figs. 2% and Lt are lviews similar to Fig. l, but showing a change in position ot certain parts of the signaling system due to the presence of a car or train at two different points on the railway. Fig. 5 is a view similar to Fig. l, but illustrating a further modification, and Figs. and 7 are detail views showing one manner of increasing the impedance of portions of the t 'ack rails.

Similar letters ot reference designate corresponding parts in all ot the figures.

In the accompanying drawings, the sources of track circuit current are shown as alternating current transformers which may be employed in all cases, whether electric propulsion is used, or not. It would be possible to use direct current sources for the track circuits if the motive power of the road were steam locomotives; but as this does not in any way affect the invention, the symbols representing the sources'of current are all those usually employed for indicating alternating current transformers.

Referring now to the drawings for a more detailed description, F ig. l represents such a system as applied to a road having electric power for propelling the trains, and the generator Gr is the source of power for the trains. @ne terminal of this generator is connected to the rails through the inductive bond a, while the other terminal is connected to the usual trolley or third rail. The connection to the bond is made at the middle point of the coil, so that the propulsion current flows in opposite directions in the two halves of the coil, and thus has no magnetizingeifect on the core of the bond. The generator G is the source of alternating current for the track circuits. This is distributed to the various points where it is to be used, through the conductors j and 7i". The transformers T, T, etc., have their primary coils 79, p, etc., connected to these mains j and 7@ in multiple. The secondaries s, s, etc., are connected to the rails r, r, in such manner that the positive terminal of s is connected to the same rail as the negative terminal of s and the positive terminal of the secondary s2 (not shown). Connected in this way, current will How from the positive terminal of s through the rail r to the negative terminal of s, thence from the positive terminal of s back through the rail r to the negative terminal of s. Current will also liow from s in the opposite direction to another secondary 82 (not shown), and back to the secondary s. So that in each secondary coil the current will divide and go in both directions through the track, one-half flowing to the right and the other one-half to the left. This distribution of current in the rails produces points of equal potential in the rails r, r, midway between two transformers. A relay, as R for instance, has its armature a connected to the rails r, r', at some distance from the equipotential points, thus having an electromotive force impressed upon it of the same sign as that of the nearer transformer and of an amount due to the product of the impedance of the rails between the points where it is connected and the equipotential points, and the amount of current flowing in the rails.

A track relay requires a certain minimum electromotive force to be applied to its coils to cause its armature to move to close the contacts, This is known as the pick-up electromotive force. In practice, it is usual to apply an electromotive force about twenty-five per cent. greater than this to secure reliable operation. This greater electromotive force may be defined as the operative electromotive force. If a resistance is placed in shunt around the relay coil and is gradually diminished, the electromotive force at the terminals of the coil will also gradually diminish. Vhen it reaches a value just a little below that required to hold the contacts closed, it is known as the shunt electromotive force. In a direct current relay, the shunt electromotive force is considerably less than the pick-up electromotive force because when the contacts are closed, the armature is closer to the magnet than when the contacts are open. Colisequently, a smaller current will' hold the contacts closed than will close them when they are open. In most alternating current relays, however, the shunt and pick-up electromotive forces are equa-l, and for the purpose of this specification in which alternating current relays are assumed to be used, l will consider these two electromotive forces equal. It' the electromotive force required at the terminals of the relay is known and if the current flowing in the rails Yfrom the transformer T and the impedance of the rails are known, then the distance at which the relay must be connected from the equipotential points becomes determinate. The distance required to cause the operative electromotive force to be impressed on the relay may b-e known as the operative distance, and it is in this sense that I have used this term in the appended claims. This distance is represented in F ig. l by the space between the points where the relay armature leads are connected to the rails and the points marked o o. The shunting distance may be defined as the distance between the connections of the relay to the rail and the points where a pair of wheels rests on the rails when the shunt voltage is applied to the relay. This distance is represented in F ig. l by the letters r r and is about fourfifths of the distance between the relay connections and the points 0 0, assuming thattlie operative electromotivey force is twentytive per cent. greater than the shunt electromotive force.

The figures on the drawing near the rail, having a plus or minus sign prefixed, are in tended to indicate potentiala The electro* motive force ofa transformer secondary is assumed to be l() volts. The connection of the positive terminal to the rail is marked plus and that of the negative terminal minus There will be a fall of potential from the point plus 5 where the positive terminal of the secondary s is connected, of t volts, to the point plus l where one terminal of the armature a is connected. A further fall of l volt occurs between point plus l and the point marked 0. From this to the connection of the negative terminal of the secondary s, there is a still further fall of 5 volts, making the potential minus The positive terminal of the secondary s' has a potential plus 5; and from this to the point marked o there will be a fall of 5 volts to zero potential. From this to the other terminal of the relay armature a there will be a fall of l volt, making the potential of this terminal minus l. From thence to the negative terminal of the secondary s a fall of 4L volts makes the potential minus 5. This distribution of potential impresses an elect-romotive force of 2 volts on the relay arma ture a. These figures are hypothetical and are merely used as illustration. The potential may have any values Within reasonable limits.

rlhe relay has two elements, one of Which may be termed the armature and the other the field, which when energized coact to produce rotation of the armature. The field f of the relay is energized directly from the signaling mains j, 7c. The current in the armature must bear a certain relation as to 'frequency and direction, to this current in the lield, in order to produce the rotation of the armature. If the current in the armature is reversed in direction with reference to the current in the field, then the armature will move in the opposite direction. Such a relay may be said to be polarized, and it is necessary with this system to use such a re lay. lf the frequency of the current in the armature differs from that in the field, n0 motion will be imparted to the armature. rllhis feature, therefore, makes the relay safe against being energized by the propulsion current, because it is either direct current or alternating current of a dilferent frequency from that employed in the signaling mains. If no current at all flows in the armature, then there will be no tendency to rotate, and the armature `will assume a middle posit-ion due to the action of a weight, or other means, so that neither pair of contacts will be closed. The circuit for any signal, as S, will be taken through a pair of contacts e, on the relay R, which are normally open, and another pair of contacts, (l, on the relay R which are normally closed. A source of current, B, supplies current for actuating the signal when the signal circuit is closed. rlhis may be either a primary battery, or the signal operating current might be taken directly from the signaling mains, y', 7u, if desired.

Normally, all the signaling circuits will be open and the signals will stand in the danger' position, as shown in Fig. l. lf a train should approach, moving in the direction of the arrow, and should reach the point to which the armature of the relay R2 is connected, it will evidently cut off all current from this armature and it will assume its middle position, due to the weight, so as to not close either' the contacts c2 or (Z2. It is also evident that the equipotential point will be at the points of the rails bridged by the wheels and axles of the train, because current from the transformer secondary in the rear of the train cannot flow past the train, and current from the secondary s will flow to the train. When the train reaches the points o, 0, it is evident that no ellect will be produced on any of the apparatus ahead of the train, because these points are normally cquipotential points, and bridging them by means of a conductor of no resistance would. have no effect on the distribution of current. As the train approaches the transformer T, the equipotential point follows it, and the potential of the secondary s falls on account of the dccreased impedance in this circuit. As the potential of the secondary s falls, the equipotent-ial points, o, o, will move toward it, and as the train approaches the transformer the equil'lotential points will approach the connection of the relay armature a. Then the equipotential points o, 0 reach the points where this armature is connected, the armature will be denergized and the contacts d disconnected, As the train approaches still closer to the transformer T, the equipotential points o, o will pass the relay connections and lie between these connections and the transfermer T. ln this position of the equipotential points o, o', the current through the relay armature o will be the reverse of that shown in the diagram, so that the contacts c will be closed, thus closing the circuit of signal S, which will then assume the clear position. lVhen the train arrives at the transformer T, the equipotential points 0, o" will meet it there. The relay armature a will still be negatively energized (if we agree to term the normal energization positive), and the signal b' will still remain clear. As the train moves on and approaches the relay lt', the cquipotential point moves with it, and when it arrives at a point somewhat nearer to the re lay than the distance normally between thc relay and the equipotcntial points, but on the opposite side of the relay, the armature o will be deenergized and go to the middle position. thus opening the circuit of the signal S, permitting it to go to the danger position but still without clqsing the circuit of the signal S on the contacts (Z. lVhen the rear of the train passes the relay and reaches the points o, o', the relay will again be normally energized and close the contacts d preparatory to the next operation of the signal S.

In tracing out the effects of the moving train on the relays, it is seen that the circuit of signal S has been opened a considerable fili time before the opening'in the circuit of the signal S at CZ has been closed. This time .is that which elapses between the arrival of the front end of the train at the points r, r at the right of the relay R, and the arrival of the rear end of the train at the points 0, o. There will always, therefore, be one or two signals showing danger behind the train.

rThe current in the relay armature is reversed by shifting the equipotential point from one side of the relay to the other. N ormally, without a train on any part of the track, the equipotential points are all on the same side of the relay, shown in the drawing as being at the left of the relay. The relay armat-ures, therefore, all stand in the saine position, thus holding one pair of contacts in each signal circuit closed, and the other pair of contacts in each signal circuit open. The signals, therefore, all stand normally in the danger position. l.When a train approaches a track circuit to which a relay is connected, it causes the equipotential point to be shifted to the opposite side of the relay connections and the current to be reversed in the relay armature. This reverses the position of the armature and opens the signal contacts, which are normally closed, and closes the other pair which are normally open. The closing of the normally open contacts clears the signal ahead of the train. The equipotential pointis shifted back to the other side of the relay into its normal position by the action of the train on the same track circuit as it recedes from it.

Since the eleotromotive force which energizes the relay armature is dependent upon the impedance of the rails between the armature and the equipotential points, or between the armature and the approaching train, where the traffic is dense and short blocks are necessary, it is desirable to have the impedance as great as possible between these points, so to permit the train to approach very close to the relay before shunting it. This is shown in Fig. 2; and in Figs. 6 and l show one form of means for increasing the impedance of the rail. This consists of a mass of iron surrounding as much as possible of the rail and is preferably laminated to prevent eddy currents and to prevent the signaling current leaving the rail and flowing through these masses of iron. Fig. 6 shows a side elevation of the rail, with the masses of iron added between the ties. Fig.

7 is a sectional View of the rail showing the ironsurroiuiding all of the rail except the part touched by the tread of the wheel. By these means l am enabled to increase the iinpedance of the rail about live times its normal amount, and with a given current in the rail the train can approach to within one-fifth of the distance before shunting the relay that it could without these masses of iron, which, for convenience, may be termed impeders. Any variations in the shunting point of therelay which might be due to variations in conditions of the track will therefore be reduced to one-fth their normal amount by the addition of these impeders.

lllhere the blocksmay be long, the normal impedance of the rails alone may be depended upon, as in such cases the required distance of the relays from the equipotential points will be only a small percentage of the total length of the blocks.

Fig. 2 is similar to Fig. l, but shows the addition of the impeders g, g to the rails on the side of the relay toward the approaching` train.

Fig. 3 is the same as Fig. 1, but shows a pair of wheelsand an axle between the transformer T and the relay R, which shows that the current flowing in the relay armature a is the reverse of that shown in Fig. l. F ig. t is the same, but showing a pair of wheels and an axle at the point where the terminals of the armature a are connected. This armature is shown in its middle position, opening both the contacts e and d. The train in this position, however, does not affect the distribution of current ahead of it.

Tt'is desirable, and in fact necessary, to connect the two rails together at intervals for the purpose of leading in or out the propulsion current from a feeder or from another track. Fig. 5 shows a means for doing this. Inductive bonds a, n, n2, etc., are connected across the rails at the same points where the relays are connected and the propulsion current is led into these inductive bonds t irough the conductors Z, Z', etc., which are connected to the middle points of the bonds for the purpose of balancing the current in the bond. These bonds offer suflicient reactance to the alternating track circuit current to permit the relay to receive suflicient current to make it operative. They also do not interfere with the movenient of the equipotent-ial point from one side of the relay to the other.

The method above described of connecting the sources of current to the track affords a ready means for reversing the current through a relay automatically by the movements of a train and without the use of circuit breakers of any kind.

I claim :m

l. ln a continuous rail signaling system, rails which are conductively continuous for all currents, sources of supply for signaling currents connected to the rails to produce shiftahle points of equal potential in the two rails between the sources of supply, and a polarized signal controlling relay connected to the track rails at the operative distance u from the normal position of each pair ot equipotential points substantially as described.

2. In a continuous rail signaling system, rails which are conductively continuous for all currents, sources of supply for signaling currents connected to the rails to produce points of equal potential in the two rails between the sources of supply, and a polarized relay having one ot' its elements connected across the track rails at the operative distance from each pair ot equipotential points and whereby the current flowing through such element is reversed by the movement of trains; substantially as described.

3. In an electric signaling system, track rails which are electrically continuous for both signalingand propulsion currents, and which are of substantially uniform impedance throughout, sources of supply for signaling currents, adjacent sources being oppositely connected to the track rails to provide shiftable points of equal potential in said rails between such sources, and polarized signal-controlling relays each having a winding connected across the track rails at the operative distance from the normal position ot' a pair of the points of equal potential; substantially as described.

4. In an electric signaling system, electrically continuous track rails, sources of supply for signaling currents connected to said rails, adjacent sources of supply being oppositely connected to the rails to produce points ot' equal potential intermediate such sources, polarized relays having windings connected across the rails at the operative distance from each pair of equipotential points, and two signal controlling circuits controlled by each relay; substantially as described.

5. In an electric signaling system, electrically continuous track rails. sources of current. supply connected to said rails, adjacent sources ot' supply having their unlike poles connected to the same rails to thereby produce shiftable points of equal potential intermediate the adjacent sources, and a polarized relay having an element connected across said rails between two such sources of supply, and at one side of the normal points ot' the equipotential; substantially as described.

6. In an electric signaling system, electrically continuous track rails, sources of supply for signaling current connected to the rails to produce points of equal potential between adjacent sources, relays having each a winding connected to the track rails at the operative distance from the corresponding pair of equipotential points, signals for two different blocks, and controlling circuits Jfor said signals both cont-rolled by one relay; substantially as described.

7. In an electric signaling system, electrically continuous track nils, sources of supply tor signaling current connected to the rails to produce shii'table points ot' equal potential between adjacent sources, polarized relays having each a winding connected tothe track rails at the operative distance ltrom the normal position oi a pair of the points oiE equal potential, signals for two diil'erent blocks at opposite sides of the normal position of each of the pairs of points ol? equal. potential, and controlling circuits for said signals, each circuit extending between two relays and arranged to be opened by either relay; substantially as described.

S. In an electric signaling system, signals for two adjacent blocks, controlling circuits 'for said signals, and a polarized relay having one position in which it closes one of such circuits, and a second position in which it closes the other circuit; substantially as described.

9. In an electric signaling system, signals tor two adjacent blocks, controlling circuits for said signals, and a polarized relay having one position in which it closes one of such circuits, and a second position in which it closes the other circuit and also a deenergized intermediate position in which it opens both circuits; substantially as described.

'l0. In an electric signaling system, electrically continuous track rails, transformers for supplying signaling current to the track rails, adjacent transformers being oppositely connected to the rails to produce points of equal potential intermediate adjacent transformers, signal controlling relays each having a winding connected across the rails near one end of a block and at the operative distance from the points of equal potential` and two signal controlling circuits controlled by each relay; substantially as described.

11. In an. electric signaling system, tra ck rails which are electrically continuous for both signaling and propulsion currents, and which are of substantially uniform impedance throughout, sources ot' supply for signaling currents, adjacent sources being oppositely connected to the track rails to provide shiftable points of equal potential in said rails between such sources, and polarized signal-controlling relays each having a winding connected across the track rails at the operative distance from the normal position ot the points of equal potential; substantially as described.

1Q. In an electric signaling system, electrically continuous track rails, transformers for supplying signaling current to the track rails, adjacent transformers being oppositely connected to the rails to produce points of equal potential intermediate adjacent transtormers, signal controlling relays each having a winding connected across the rails near one `end of a block and at the operative distance Vfrom the points of equal potential, and two signal controlling circuits controlled by each relay, .together with cross connections between the .rails;,

` nected `to the rails to produce points of substantially Aas described.

13. In an electric signaling system, .elec-- trically continuous track rails, transformers for supplyingsignaling current .to the track rails, adjacent vtransformers being `oppo-` sitely connected to the rails to .produce points of equal potential intermediate 1adjacent transformers, signal controlling rea,y

lays each vhaving a winding connected|` across the rails near yone lend of .one block; and kat the .operative :distance from the points yof equal ,potential, and `two sign-alg' controlling circuits `controlled lby each -re-i` lay, together with cross connect-ions befl tween .the raifls .and ,to which lathe connections for the propulsion current are connectedg.

substantially as described.

14. .In an electric signaling system, -elecj trlcally continuous track rails, transformers for supplying `signaling current to the track rails, adjacent transformers being oppositely connected to therailsto-producegpoints of equal potential intermediate -fad-jaeent transformers, `signal controlling :relayseach having a winding connected across the :rails near one -end of Aone :block )and Yat `the 4operative distance "fromfthe points 'of-equal -potential, and ftwo signal controlli-ng circuits controlled by'each frelay, and an inductive 'bond connecting the track l:rails adjacent :to the relays and to which vthe connections for :the propulsion current are made; substantially as described.

15. In an Velectric signaling system, a polarized relay having a winding connected to the track rails across one end port-ion of a block, a track circuit including said rails, two sources of current oppositely conequipo-tential therein which are shifted by t-he passage of trains to opposite sides of the connections of said winding, and two signal circuits controlled by such relay, substantially Vas described.

16. In a continuous rail signaling Asystem, rails which :are conductively continuous vfor all currents, sources of supply for signaling currents connected to the rails to produce pointsof equal potential in the two yrails between the sources o-f supply and a polari-Zed signal control-.linggrelay connected to .the track rails Aat the opera-tive distance from each pair of points of equal potential .and vat that' side only of such points in the direction from which trains approach -the relays; substantially as described.

17. In an electric signaling system, sources yofsupply for -signaling current connected to the track rails to lproduce points of equal `potential in t-he rails Vintermedi-ate adjacent sources, yand 4relays connected to the track rails Eat the yoperative distance Afrom the points of -equal ,potential and Aon the side of approaching traflic only; substantial-ly as described.

In testimony whereof, I have hereunto set my hand.

JOHN D. TAYLQR. Witnesses:

M. ConwIN, .Gno. II. PAR-MELEE.

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